/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_fir_interpolate_f32.c
*
* Description:	FIR interpolation for floating-point sequences.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated
*
* Version 0.0.7  2010/06/10
*    Misra-C changes done
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @defgroup FIR_Interpolate Finite Impulse Response (FIR) Interpolator
 *
 * These functions combine an upsampler (zero stuffer) and an FIR filter.
 * They are used in multirate systems for increasing the sample rate of a signal without introducing high frequency images.
 * Conceptually, the functions are equivalent to the block diagram below:
 * \image html FIRInterpolator.gif "Components included in the FIR Interpolator functions"
 * After upsampling by a factor of <code>L</code>, the signal should be filtered by a lowpass filter with a normalized
 * cutoff frequency of <code>1/L</code> in order to eliminate high frequency copies of the spectrum.
 * The user of the function is responsible for providing the filter coefficients.
 *
 * The FIR interpolator functions provided in the CMSIS DSP Library combine the upsampler and FIR filter in an efficient manner.
 * The upsampler inserts <code>L-1</code> zeros between each sample.
 * Instead of multiplying by these zero values, the FIR filter is designed to skip them.
 * This leads to an efficient implementation without any wasted effort.
 * The functions operate on blocks of input and output data.
 * <code>pSrc</code> points to an array of <code>blockSize</code> input values and
 * <code>pDst</code> points to an array of <code>blockSize*L</code> output values.
 *
 * The library provides separate functions for Q15, Q31, and floating-point data types.
 *
 * \par Algorithm:
 * The functions use a polyphase filter structure:
 * <pre>
 *    y[n] = b[0] * x[n] + b[L]   * x[n-1] + ... + b[L*(phaseLength-1)] * x[n-phaseLength+1]
 *    y[n+1] = b[1] * x[n] + b[L+1] * x[n-1] + ... + b[L*(phaseLength-1)+1] * x[n-phaseLength+1]
 *    ...
 *    y[n+(L-1)] = b[L-1] * x[n] + b[2*L-1] * x[n-1] + ....+ b[L*(phaseLength-1)+(L-1)] * x[n-phaseLength+1]
 * </pre>
 * This approach is more efficient than straightforward upsample-then-filter algorithms.
 * With this method the computation is reduced by a factor of <code>1/L</code> when compared to using a standard FIR filter.
 * \par
 * <code>pCoeffs</code> points to a coefficient array of size <code>numTaps</code>.
 * <code>numTaps</code> must be a multiple of the interpolation factor <code>L</code> and this is checked by the
 * initialization functions.
 * Internally, the function divides the FIR filter's impulse response into shorter filters of length
 * <code>phaseLength=numTaps/L</code>.
 * Coefficients are stored in time reversed order.
 * \par
 * <pre>
 *    {b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]}
 * </pre>
 * \par
 * <code>pState</code> points to a state array of size <code>blockSize + phaseLength - 1</code>.
 * Samples in the state buffer are stored in the order:
 * \par
 * <pre>
 *    {x[n-phaseLength+1], x[n-phaseLength], x[n-phaseLength-1], x[n-phaseLength-2]....x[0], x[1], ..., x[blockSize-1]}
 * </pre>
 * The state variables are updated after each block of data is processed, the coefficients are untouched.
 *
 * \par Instance Structure
 * The coefficients and state variables for a filter are stored together in an instance data structure.
 * A separate instance structure must be defined for each filter.
 * Coefficient arrays may be shared among several instances while state variable array should be allocated separately.
 * There are separate instance structure declarations for each of the 3 supported data types.
 *
 * \par Initialization Functions
 * There is also an associated initialization function for each data type.
 * The initialization function performs the following operations:
 * - Sets the values of the internal structure fields.
 * - Zeros out the values in the state buffer.
 * - Checks to make sure that the length of the filter is a multiple of the interpolation factor.
 *
 * \par
 * Use of the initialization function is optional.
 * However, if the initialization function is used, then the instance structure cannot be placed into a const data section.
 * To place an instance structure into a const data section, the instance structure must be manually initialized.
 * The code below statically initializes each of the 3 different data type filter instance structures
 * <pre>
 * arm_fir_interpolate_instance_f32 S = {L, phaseLength, pCoeffs, pState};
 * arm_fir_interpolate_instance_q31 S = {L, phaseLength, pCoeffs, pState};
 * arm_fir_interpolate_instance_q15 S = {L, phaseLength, pCoeffs, pState};
 * </pre>
 * where <code>L</code> is the interpolation factor; <code>phaseLength=numTaps/L</code> is the
 * length of each of the shorter FIR filters used internally,
 * <code>pCoeffs</code> is the address of the coefficient buffer;
 * <code>pState</code> is the address of the state buffer.
 * Be sure to set the values in the state buffer to zeros when doing static initialization.
 *
 * \par Fixed-Point Behavior
 * Care must be taken when using the fixed-point versions of the FIR interpolate filter functions.
 * In particular, the overflow and saturation behavior of the accumulator used in each function must be considered.
 * Refer to the function specific documentation below for usage guidelines.
 */

/**
 * @addtogroup FIR_Interpolate
 * @{
 */

/**
 * @brief Processing function for the floating-point FIR interpolator.
 * @param[in] *S        points to an instance of the floating-point FIR interpolator structure.
 * @param[in] *pSrc     points to the block of input data.
 * @param[out] *pDst    points to the block of output data.
 * @param[in] blockSize number of input samples to process per call.
 * @return none.
 */
#ifndef ARM_MATH_CM0

/* Run the below code for Cortex-M4 and Cortex-M3 */

void arm_fir_interpolate_f32(
    const arm_fir_interpolate_instance_f32* S,
    float32_t* pSrc,
    float32_t* pDst,
    uint32_t blockSize)
{
	float32_t* pState = S->pState;                 /* State pointer */
	float32_t* pCoeffs = S->pCoeffs;               /* Coefficient pointer */
	float32_t* pStateCurnt;                        /* Points to the current sample of the state */
	float32_t* ptr1, *ptr2;                        /* Temporary pointers for state and coefficient buffers */
	float32_t sum0;                                /* Accumulators */
	float32_t x0, c0;                              /* Temporary variables to hold state and coefficient values */
	uint32_t i, blkCnt, j;                         /* Loop counters */
	uint16_t phaseLen = S->phaseLength, tapCnt;    /* Length of each polyphase filter component */
	float32_t acc0, acc1, acc2, acc3;
	float32_t x1, x2, x3;
	uint32_t blkCntN4;
	float32_t c1, c2, c3;

	/* S->pState buffer contains previous frame (phaseLen - 1) samples */
	/* pStateCurnt points to the location where the new input data should be written */
	pStateCurnt = S->pState + (phaseLen - 1u);

	/* Initialise  blkCnt */
	blkCnt = blockSize / 4;
	blkCntN4 = blockSize - (4 * blkCnt);

	/* Samples loop unrolled by 4 */
	while(blkCnt > 0u) {
		/* Copy new input sample into the state buffer */
		*pStateCurnt++ = *pSrc++;
		*pStateCurnt++ = *pSrc++;
		*pStateCurnt++ = *pSrc++;
		*pStateCurnt++ = *pSrc++;

		/* Address modifier index of coefficient buffer */
		j = 1u;

		/* Loop over the Interpolation factor. */
		i = (S->L);

		while(i > 0u) {
			/* Set accumulator to zero */
			acc0 = 0.0f;
			acc1 = 0.0f;
			acc2 = 0.0f;
			acc3 = 0.0f;

			/* Initialize state pointer */
			ptr1 = pState;

			/* Initialize coefficient pointer */
			ptr2 = pCoeffs + (S->L - j);

			/* Loop over the polyPhase length. Unroll by a factor of 4.
			 ** Repeat until we've computed numTaps-(4*S->L) coefficients. */
			tapCnt = phaseLen >> 2u;

			x0 = *(ptr1++);
			x1 = *(ptr1++);
			x2 = *(ptr1++);

			while(tapCnt > 0u) {

				/* Read the input sample */
				x3 = *(ptr1++);

				/* Read the coefficient */
				c0 = *(ptr2);

				/* Perform the multiply-accumulate */
				acc0 += x0 * c0;
				acc1 += x1 * c0;
				acc2 += x2 * c0;
				acc3 += x3 * c0;

				/* Read the coefficient */
				c1 = *(ptr2 + S->L);

				/* Read the input sample */
				x0 = *(ptr1++);

				/* Perform the multiply-accumulate */
				acc0 += x1 * c1;
				acc1 += x2 * c1;
				acc2 += x3 * c1;
				acc3 += x0 * c1;

				/* Read the coefficient */
				c2 = *(ptr2 + S->L * 2);

				/* Read the input sample */
				x1 = *(ptr1++);

				/* Perform the multiply-accumulate */
				acc0 += x2 * c2;
				acc1 += x3 * c2;
				acc2 += x0 * c2;
				acc3 += x1 * c2;

				/* Read the coefficient */
				c3 = *(ptr2 + S->L * 3);

				/* Read the input sample */
				x2 = *(ptr1++);

				/* Perform the multiply-accumulate */
				acc0 += x3 * c3;
				acc1 += x0 * c3;
				acc2 += x1 * c3;
				acc3 += x2 * c3;


				/* Upsampling is done by stuffing L-1 zeros between each sample.
				 * So instead of multiplying zeros with coefficients,
				 * Increment the coefficient pointer by interpolation factor times. */
				ptr2 += 4 * S->L;

				/* Decrement the loop counter */
				tapCnt--;
			}

			/* If the polyPhase length is not a multiple of 4, compute the remaining filter taps */
			tapCnt = phaseLen % 0x4u;

			while(tapCnt > 0u) {

				/* Read the input sample */
				x3 = *(ptr1++);

				/* Read the coefficient */
				c0 = *(ptr2);

				/* Perform the multiply-accumulate */
				acc0 += x0 * c0;
				acc1 += x1 * c0;
				acc2 += x2 * c0;
				acc3 += x3 * c0;

				/* Increment the coefficient pointer by interpolation factor times. */
				ptr2 += S->L;

				/* update states for next sample processing */
				x0 = x1;
				x1 = x2;
				x2 = x3;

				/* Decrement the loop counter */
				tapCnt--;
			}

			/* The result is in the accumulator, store in the destination buffer. */
			*pDst = acc0;
			*(pDst + S->L) = acc1;
			*(pDst + 2 * S->L) = acc2;
			*(pDst + 3 * S->L) = acc3;

			pDst++;

			/* Increment the address modifier index of coefficient buffer */
			j++;

			/* Decrement the loop counter */
			i--;
		}

		/* Advance the state pointer by 1
		 * to process the next group of interpolation factor number samples */
		pState = pState + 4;

		pDst += S->L * 3;

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
	 ** No loop unrolling is used. */

	while(blkCntN4 > 0u) {
		/* Copy new input sample into the state buffer */
		*pStateCurnt++ = *pSrc++;

		/* Address modifier index of coefficient buffer */
		j = 1u;

		/* Loop over the Interpolation factor. */
		i = S->L;

		while(i > 0u) {
			/* Set accumulator to zero */
			sum0 = 0.0f;

			/* Initialize state pointer */
			ptr1 = pState;

			/* Initialize coefficient pointer */
			ptr2 = pCoeffs + (S->L - j);

			/* Loop over the polyPhase length. Unroll by a factor of 4.
			 ** Repeat until we've computed numTaps-(4*S->L) coefficients. */
			tapCnt = phaseLen >> 2u;

			while(tapCnt > 0u) {

				/* Read the coefficient */
				c0 = *(ptr2);

				/* Upsampling is done by stuffing L-1 zeros between each sample.
				 * So instead of multiplying zeros with coefficients,
				 * Increment the coefficient pointer by interpolation factor times. */
				ptr2 += S->L;

				/* Read the input sample */
				x0 = *(ptr1++);

				/* Perform the multiply-accumulate */
				sum0 += x0 * c0;

				/* Read the coefficient */
				c0 = *(ptr2);

				/* Increment the coefficient pointer by interpolation factor times. */
				ptr2 += S->L;

				/* Read the input sample */
				x0 = *(ptr1++);

				/* Perform the multiply-accumulate */
				sum0 += x0 * c0;

				/* Read the coefficient */
				c0 = *(ptr2);

				/* Increment the coefficient pointer by interpolation factor times. */
				ptr2 += S->L;

				/* Read the input sample */
				x0 = *(ptr1++);

				/* Perform the multiply-accumulate */
				sum0 += x0 * c0;

				/* Read the coefficient */
				c0 = *(ptr2);

				/* Increment the coefficient pointer by interpolation factor times. */
				ptr2 += S->L;

				/* Read the input sample */
				x0 = *(ptr1++);

				/* Perform the multiply-accumulate */
				sum0 += x0 * c0;

				/* Decrement the loop counter */
				tapCnt--;
			}

			/* If the polyPhase length is not a multiple of 4, compute the remaining filter taps */
			tapCnt = phaseLen % 0x4u;

			while(tapCnt > 0u) {
				/* Perform the multiply-accumulate */
				sum0 += *(ptr1++) * (*ptr2);

				/* Increment the coefficient pointer by interpolation factor times. */
				ptr2 += S->L;

				/* Decrement the loop counter */
				tapCnt--;
			}

			/* The result is in the accumulator, store in the destination buffer. */
			*pDst++ = sum0;

			/* Increment the address modifier index of coefficient buffer */
			j++;

			/* Decrement the loop counter */
			i--;
		}

		/* Advance the state pointer by 1
		 * to process the next group of interpolation factor number samples */
		pState = pState + 1;

		/* Decrement the loop counter */
		blkCntN4--;
	}

	/* Processing is complete.
	 ** Now copy the last phaseLen - 1 samples to the satrt of the state buffer.
	 ** This prepares the state buffer for the next function call. */

	/* Points to the start of the state buffer */
	pStateCurnt = S->pState;

	tapCnt = (phaseLen - 1u) >> 2u;

	/* copy data */
	while(tapCnt > 0u) {
		*pStateCurnt++ = *pState++;
		*pStateCurnt++ = *pState++;
		*pStateCurnt++ = *pState++;
		*pStateCurnt++ = *pState++;

		/* Decrement the loop counter */
		tapCnt--;
	}

	tapCnt = (phaseLen - 1u) % 0x04u;

	/* copy data */
	while(tapCnt > 0u) {
		*pStateCurnt++ = *pState++;

		/* Decrement the loop counter */
		tapCnt--;
	}
}

#else

/* Run the below code for Cortex-M0 */

void arm_fir_interpolate_f32(
    const arm_fir_interpolate_instance_f32* S,
    float32_t* pSrc,
    float32_t* pDst,
    uint32_t blockSize)
{
	float32_t* pState = S->pState;                 /* State pointer */
	float32_t* pCoeffs = S->pCoeffs;               /* Coefficient pointer */
	float32_t* pStateCurnt;                        /* Points to the current sample of the state */
	float32_t* ptr1, *ptr2;                        /* Temporary pointers for state and coefficient buffers */


	float32_t sum;                                 /* Accumulator */
	uint32_t i, blkCnt;                            /* Loop counters */
	uint16_t phaseLen = S->phaseLength, tapCnt;    /* Length of each polyphase filter component */


	/* S->pState buffer contains previous frame (phaseLen - 1) samples */
	/* pStateCurnt points to the location where the new input data should be written */
	pStateCurnt = S->pState + (phaseLen - 1u);

	/* Total number of intput samples */
	blkCnt = blockSize;

	/* Loop over the blockSize. */
	while(blkCnt > 0u) {
		/* Copy new input sample into the state buffer */
		*pStateCurnt++ = *pSrc++;

		/* Loop over the Interpolation factor. */
		i = S->L;

		while(i > 0u) {
			/* Set accumulator to zero */
			sum = 0.0f;

			/* Initialize state pointer */
			ptr1 = pState;

			/* Initialize coefficient pointer */
			ptr2 = pCoeffs + (i - 1u);

			/* Loop over the polyPhase length */
			tapCnt = phaseLen;

			while(tapCnt > 0u) {
				/* Perform the multiply-accumulate */
				sum += *ptr1++ * *ptr2;

				/* Increment the coefficient pointer by interpolation factor times. */
				ptr2 += S->L;

				/* Decrement the loop counter */
				tapCnt--;
			}

			/* The result is in the accumulator, store in the destination buffer. */
			*pDst++ = sum;

			/* Decrement the loop counter */
			i--;
		}

		/* Advance the state pointer by 1
		 * to process the next group of interpolation factor number samples */
		pState = pState + 1;

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* Processing is complete.
	 ** Now copy the last phaseLen - 1 samples to the start of the state buffer.
	 ** This prepares the state buffer for the next function call. */

	/* Points to the start of the state buffer */
	pStateCurnt = S->pState;

	tapCnt = phaseLen - 1u;

	while(tapCnt > 0u) {
		*pStateCurnt++ = *pState++;

		/* Decrement the loop counter */
		tapCnt--;
	}

}

#endif /*   #ifndef ARM_MATH_CM0 */



/**
 * @} end of FIR_Interpolate group
 */
